I've been doing some investigatory work into how to bridge an existing services
system (with thousands of services) into our IEclipseContext setup. We're
dealing with potentially hundreds of such services. Here's a few things I've
discovered:
The ILookupStrategy that was backed out as a result of bug 317706 would have
been really useful. In my case, I want to hook these services into the
part/window/app level contexts. I can't create my own IEC subclass as I don't
have the opportunity to replace the class used to create child contexts. I
mentioned this on the E4 call last week and have opened bug 401931
(https://bugs.eclipse.org/bugs/show_bug.cgi?id=401931).
IContextFunction#compute() should receive the requested context key. We
explored using IContextFunctions to look up our services, but it required
creating an ICF for each service which is a bit expensive. I've filed this as
bug 401933 (https://bugs.eclipse.org/bugs/show_bug.cgi?id=401933).
For now I've instead implemented my own object supplier, which is pretty cool.
Two notes from here (and they're just documentation issues):
It's not clear how ExtendedObjectSuppliers can hook into the group-changes:
although an EOS could assume that the primary object supplier is a
ContextObjectSupplier and request to be injected with an IEclipseContext, the
EclipseContext addWaiting()/processWaiting() is internal to contexts. This
only becomes an issue if we have methods that mix custom injections and normal
context injections. And perhaps this is asking a lot anyways!
I was a bit surprised that disposing of a context doesn't uninject the fields,
and so my EOS's get() wasn't called with track=false. Rather, the
IRequestor.isValid() will return false once the injected object is GC'd. I saw
injections continuing on my disposed objects as my objects were being held
onto… by my EOS! (Inadvertent, and now fixed.)
BTW: The one gotcha to implementing a custom object supplier (any component for
Declarative Services): ensure your bundle is lazily-activated as DS otherwise
ignores the service components until that bundle is explicitly started.
Brian.
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